Most of the studies conducted in the area of physical training programs for the handicapped have concluded that there is little benefit to a systematic training program in improving the physical condition of the handicapped. As a result, there has been little work done to develop and improve physical exercise equipment available for the handicapped. Indeed, much of the equipment presently available was developed for use in studies and most designs are of limited complexity, possibly owing to the limited budgets of the studies. In the prior art, there are three types of designs which are prevalent. These include a floor mounted, motor driven treadmill which provides a moving surface over which a wheelchair may be driven by a subject, a platform having rollers which receives the wheels of the wheelchair, and a stationary wheelchair with a chain drive coupling to a bicycle ergometer. Each of these exercise devices are designed to enable a subject to remain stationary as he exercises so that proper instrumentation may be attached to the subject and data collected with a minimum amount of expense and with maximum accuracy and convenience to the experimenter. As can be appreciated, it would be very difficult to perform any sort of extended testing of a subject in a wheelchair if the wheelchair does not remain stationary relative to the instrumentation.
Each of the prior art devices has drawbacks which limit their usefulness and effectiveness as a tool in collecting data and in providing a suitable exercising device. For example, the floor mounted, motor driven treadmill does provide for use of a standard wheelchair but it can be quite expensive to install and maintain and provides a possibility of mishap should the subject either fail to keep up with the treadmill or unexpectedly leave the treadmill during an experiment or exercise bout if no restraining chains were provided. Also, the energy which the individual supplies during exercise is not measurable with the treadmill. The stationary wheelchair coupled with a chain drive to a bicycle ergometer provides a less expensive arrangement than the floor level treadmill but is not suited for accurate energy expenditure measurements due to unmeasurable energy losses involved in the gearing, bearings, and chain drive mechanism. Furthermore, there is no structure provided to compensate for the different effects of translational inertia corresponding to different mass subjects in the wheelchair.
Another prior art device is the wheelchair dynamometer; a platform having rollers which receive the wheels of the wheelchair. A brake and clutch may be mounted on the same shaft as the rollers and provide for loading the rollers, as desired, to simulate either an uphill or downhill surface, wind, terrain, etc. load. Flywheels may be added to the rollers to compensate for the translational inertia loading a subject experiences as he propels his wheelchair. A dynamometer similar to that described was constructed and used by Breur in several studies. He used cast iron, flat belt pulleys as rollers with a magnetic clutch and brake, and a variable weight flywheel connected to the rear of each pair of rollers by a drive chain. The front roller of each pair acts as an idler and provides the seating for the large drive wheels of the wheelchair. Variable weights can be added to the flywheel to compensate for the effects of different mass subjects. The brake is used to simulate non-inertial forces acting on the wheelchair. The dynamometer platform itself is not an accurate means of measuring the energy supplied by the subject since energy losses due to wheelchair bearings and wheel-roller friction are unaccounted for and thus a subject is actually performing greater work than given credit for in the data collected. As can be appreciated, Breur's device is relatively expensive and depends upon a continuous contact between the large wheels of the wheelchair and the rollers to obtain accurate results. Also, it is necessary to wheel the wheelchair and subject up an incline and into position on the rollers before measurements can be made. Also, each time a subject applies a force to the driving wheels, the tires of the wheelchair have a tendency to slip (particularly for heavy brake loads) due to the abrupt application of a torque, which increases the inaccuracy of any energy measurement.
To overcome these and other problems, applicants have succeeded in designing and constructing a stationary wheelchair ergometer which simulates the propulsion of a wheelchair and which eliminates the problems in the prior art devices and provides for more accurate measurement of the actual work expended by a subject during an exercise bout. The wheelchair ergometer simulates the propulsion of a wheelchair by having a stand or the like which elevates a chair and drive wheels above the ground so that a subject may sit in the chair and push the drive wheels as if he were propelling a standard wheelchair. Applicants' device eliminates the friction drive, gearing, and the chain coupling or other driving connections required in the prior art between the central shaft of the wheelchair and various types of loading structure. Applicants' device essentially includes a friction type brake which is clamped to the central shaft of a wheelchair and is also attached to a torque platform which pivots or deflects in relation to the amount of load torque applied to the central shaft. Flywheels are provided at the outer ends of the central shaft and are loaded with weights to compensate for the translational inertia of a rolling wheelchair and subject. A speedometer hook up and revolution counter is provided which measures the speed of the shaft and the distance traveled during exercise bouts which provides sufficient information from which to calculate the energy expended by a subject and also monitor the rate of performance.
Applicants' device is an elegantly simple self contained unit which eliminates much of the heavy expensive structure required in the prior art devices and which also improves the accuracy of subject energy expenditure measurements. Ball bearings and needle bearings support the torque measuring platform from the frame which under steady state operating conditions does not rotate; thus minimizing error in measuring all other torques (i.e. brake and wheelchair bearing torques) which convert the energy supplied by the subject to measurable energy. This bearing support effectively isolates the torque platform from the frame and also minimizes error for those measurements and exercise routines utilizing a moving torque platform. This helps ensure that a subject is credited for all the energy supplied in performing an exercise bout. Furthermore, torque is measured before it has been transmitted through a series of gears of chain drives as in the prior art. Other features include a counterbalance and tilting scale for calibration of torque readout, magnetic pickups to measure speed and count the number of revolutions, and a unique flywheel compensation system to apply an equivalent translational inertia to the wheelchair.
Applicants' wheelchair ergometer has been used in a study with results indicating that wheelchair confined subjects may be substantially benefitted by regular exercise to improve their physical conditioning. It is anticipated that other studies will confirm these results and that there will be a great demand for applicants' wheelchair ergometer for use as an exercise device, as well as for instrumentation in further experiments. These and other features of applicants' invention may be more fully understood by referring to the drawings and description of the preferred embodiment.